Float switch with explosion-proof chamber



Feb. 2, 1965 R. w. HILL 3,168,625

FLOAT SWITCH WITH EXPLOSION-PROOF CHAMBER Filed Aug. 8, 1962 INVENTOR RALPH W. H l LL ATTORNEYS United States Patent O a .it

amants FLAT SW id/ETH EXPLGSlON-PROF tCiAlldlI-ER Ralph W. Hill, 2163 S. Sandusky, Tulsa, Dida. Filed Aug. ti, 1962, Ser. No. 215,796 Claims. (Cl. 20D-84) This invention relates to a tlo'at switch. More particularly, the invention relates to a iloat switch for mounting on the side of a vessel, the float switch being identitied by an improved sealing and pivoting means and improved means of providing an explosion proof enclosure. Still more particularly, the invention relates to a float switch for mounting on the side oi a vessel including means utilizing a flexible diaphragm as a seal and including means of providing an explosion proof housing in which the switch components are located.

Float switches are in frequent use in all phases of industry. The most common use of iloat switches is to detect liuid level in a vessel. Typically the iloat switches are mounted on the side of a vessel and have a pivoted rod with a tloat on the end thereof leading inside the vessel so that, as iluid raises or lowers past the float, pivotal movement is imparted to the rod for the actuation of a switch.

In the oil and chemical industry it is frequently necessary to provide an explosion proof enclosure for the switch portion so that any explosion or ignition of combustible mixtures occasioned by electrical sparks in the switch enclosure is not conveyed into the interior of the vessel to which a switch is attached. This has presented a difficult problem. There are several ways in which an explosion proof enclosure may be maintained, but all of the known means include relatively expensive mechanisms, or mechanisms which require periodic maintenance, or which have a more or less limited useful lite.

It is therefore `an object of this invention to provide a lloat switch which is explosion proof.

Another object of this invention is to provide a float switch which has improved sealing means to prevent the leakage of iluid from the vessel, to which the float is attached, into the switch compartment.

Other objects of this invention include the provision of a tloat switch which is inexpensive to manufacture, which has no wearing parts subject to sticking from paraihn accumulation or corrosion, which is simple in installation, which has no adjustments to get out of order or to be misadjusted, which may be simply repaired and which has no stuiilng boxes or stuffing box packing, which has no llexible metal seals to fatigue and which therefore is of long land substantially trouble-free life.

These and other objects and a better understanding of the invention may be had by referring to the following description and claims tal-:en in conjunction with the attached drawings in which:

FlGURE 1 is a cross-sectional view of the iloat switch of this invention as the switch is mounted on a vessel.

FGURE 2 is a cross-sectional View taken along the line 2-2 of FIGURE l.

FEGURE 3 is a cross-sectional view taken along the line 3-3 of FGURE l.

This invention may be described as a float switch having improved pivot rod support means and improved explosion, proof sealing means. More particularly, but not by way of limitation, this invention may be described as an explosion-proof switch adapted to be supported to the wall of a vessel at an opening in said wall comprising in combination: a closed explosion-proof chamber having an opening in one wall, said closed chamber adaptable to be supported to said vessel at said opening in said wall; a diaphragm member adjacent said wall of said closed chamber, said diaphragm member sealing the interior of said vessel `from the interior of said closed chamber; a rod extending through said opening in said Vessel and said opening in said closed chamber, said rod pivotably supported by said diaphragm member; a switch means supported within said chamber actuated by pivotation of said rod; and a shield flange supported to said rod within said closed chamber adjacent said opening in said closed chamber, said shield ilange of an area larger than the area of said opening in said closed chamber, said shield harige engageable with said wall of said closed chamber around the total periphery of said opening therein when pressure in said closed chamber rises.

Referring iirst to FIGURE l, the iioat switch of this invention is indicated generally by the numeral 1li. The iloat switch lt) is shown in a typical attitude of use as a'ixed to the exterior of the wall l2 of a vessel, the wall of the vessel having an opening 14 therein. Typically, the float switch l@ is installed on a vessel by welding a half coupling i6 to the wall l2 of the vessel, the coupling i6 being welded to fully surround the opening 14. The half coupling le threadably receives a short length of p adaptor nipple lll, which may be of the typically available grooved type adaptable to receive at the end thereof a groove type coupling 2t?. Coupling 2t? is usually provided with a gasket 22 to form a quick mountable pressure sealed coupling.

A grooved tubular body member 24 of a diameter adapted to receive coupling 2i? supports the iloat switch housing 26, as by means of bolts 2S.

The switch housing 26 includes the switching mechanisms, as will be hereinafter described, and is closed by a cover 39 threadably engaging the housing 26 so that the housing presents an explosion proof enclosure capable of withstanding and containing, without rupture, the force of an explosion which may occur due to the accumula- `ion of an explosive mixture therein and the ignition of the explosion mixture as might occur by electrical sparks caused by the making and breaking or switch contacts or by a short circuit. A hub 32 integrally formed with the housing Z6 provides means for connecting a conduit to the housing whereby electrical conductors may enter the housing.

Fluid level is detected in the vessel to which the i'loat switch 1t) is attached by a iioat 34 which is iioated upwardly as fluid level rises past the iloat switch 1G and is lowered downwardly as the iluid level lowers past the float switch l0. Float is ailixed to the end of a pivot rod 36. Sealing the interior of housing 26 from the interior of tubular body member 2d, and thereby the interior of the vessel 12, is a diaphragm member 3S. Diaphragm 3S sealably receives, in the center thereof, pivot rod 36. The forward wall 3S* of housing Zd is provided with `an opening lil through which pivot rod 36 extends. Nuts f-i-lA and ilB secured to rod 35 firmly support rod 36 to the diaphragm 38 so that the diaphragm serves as the pivot point for rod 36. Nuts dlA and 41B may be affixed to rod 36 in a variety of ways. For instance, nut 41A may be integrally formed or otherwise securely atlixed to rod 3d while nut iB may be threaded onto rod 36 for easily securing the rod to the diaphragm.

Afiixed at one end of pivot rod 36 witmn housing 25 is a shield flange i2 iirmly held to rod 3e and against nut tB by a nut 44. The shield flange d?. is provided with an integrally formed extending switch support leg 46 which extends to actuate a switch.

The switch support leg 46 may actuate any usual type of switch, such as a micro-switch, but the preferred embodiment includes a clip 43, supported to the switch support leg 46 by bolt Sti, which holds a mercury switch Positioned parallel to each other and adjacent to and to each side of shield flange 42 is a rst and second alogene connection block '54A and 54B (see FIGURES 2 and 3). Connection blocks 54A and 54B are secured to the forward wall 39 of housing 26, as by means of bolts 56. To prevent accidental contact with conductors, connection blocks 54 are provided with recessed areas 58 in which the heads of bolts 56 are recessed.

Connection points 6) are provided on the connection blocks 54A and 54B to furnish means whereby conductors (not shown) extending from mercury switch 52 may be easily connected to conductors (also not shown) extending to the float switch it) through hub 52.

Shield flange 42 may be provided with a vertically extending upper stabilizing leg 62. Connection blocks 54A and 54B positioned adjacent to and to either side of shield flange 42 serves an ancillary purpose, in conjunction with the switch support leg 46 and stabilizer leg 62, to restrain the pivotal movement of rod 36 to a vertical plane.

Diaphragm 38 may be composed of any exible material having the qualities of strength and chemical re sistance to the material encountered in the vessel to which the switch is attached. Although a variety of materials may be utilized for diaphragm 38, no single material has been found Which accomplishes the desired results for most effective use in the petroleum and chemical industry. An elastomer material known by the tradename of Hycar has the necessary physical strength and flexibility to provide the function of pivotally supporting pivot rod 36 but this material has been found to be non-resistant to certain chemicals encountered in industry, especially in the petroleum industry. it has been learned thatV the desirable characteristics of the strong, highly fiexible Hycar material may be effective- Vly utilized by the provision of a chemical resistant flexible protective sealing sheet. Such a seal sheet or liner may be composed of a plastic material known by the tradename Teflon In FGURE 1 the Hycar elastomer diaphragm is indicated at 64 with the Teflon liner indicated at 66. The combination of the Teflon liner 66 and the Hycar elastomer diaphragm 64 together produce a highy superior diaphragm 38. The Teon material of which liner 66 is formed is not sufficiently flexible in thicknesses required for the necessary strength to provide stable physical support of rod 36, but the Teon7 material is highly resistant to chemical attack by most chemicals encountered in the petroleum and chemical industries. Thus, the combination of the Teflon liner 66 and the Hycar elastomer diaphragm 64 provides a total diaphragm 38 having all of the desired characteristics not found in any other single material.

ln its simplest embodiment it can be seen that the diaphragm member 38 could be positioned in direct engagement with vessel wall 12, provided the vessel wall l2 was fiat at the area of contact with diaphragm 38 so that it conforms with the forward wall 39 of housing 26. In other Words, the half coupling 16, the adaptor nipple 18, the coupling 20 and the tubular body member 24 are not essential to the essence of the invention although at least the tubular body member 24 will normally be a component of the switch, the other components being readily available on the open market.

Operation When liquid rises within the vessel 12, float 34 is floated upwardly, pivoting rod 36, which pivots about the diaphragm 38, to in turn pivot the -attached switch support leg 46 for the actuation of mercury switch 52. Diaphragm 38 serves not only as a pivotal support for rod 36 but as a seal to prevent the escape of liquids and gases from within the vessel 12. Connection blocks 54A and 54B, as best shown in FIGURES 2 and 3, serve to keep in proper alignment shield ange 42. The vertically extending switch support leg 46 and the stabilizing leg 62 positioned between the paralleled switch blocks 54A and 54B permit unrestrained vertical pivotation of rod 36. By restricting the movement of pivot rod 36 to a vertical plane shield flange 42 is maintained in substantially parallel alignment with forward wall 39 of housing 26 at all times.

If an accumulation of explosive gas occurs within housing 26 and for some reason a spark occurs within the housing (although the chance of the occurrence of a spark is substantially minimized by the use of mercury switch 52 rather than an open contact switch) the switch of this invention functions in a unique way to prevent Vthe explosion from being communicated to the interior of the vessel l2. As initial pressure is built up as a result of the explosion, pressure on diaphragm 38 moves it outwardly bringing shield flange 42 into engagement with the forward wall 39 of housing 26 so that a metal to metal Contact around the total circumference of opening 46 in housing 26 is obtained. As the pressure of the explosion continues to build, the metal to metal Contact of the shield flange 42 against forward wall 39 reduces, or at best completely eliminates, further cornmunication of the explosive force with diaphragm 38. Even though the metal to metal contact between shield flange 42 and forward wall 39 might be imperfect, the transmittal of the full effect of an explosion within housing 26 to diaphragm 38 is retarded so that the peak pressure of the explosion is prevented from reaching diaphragm 33. Y

All laboratory tests wherein explosions have been intentionally introduced within housing 26 have shown that the -action of the shield flange 42 engaging forward wall 39 to seal opening 40 has been completely effective to prevent the rupture of diaphragm 38. v

It can be seen that the diaphragm 38 could be placed on the inside of housing 26 adjacent forward wall 39. In this arrangement the nut 41B would not be utilized and the shield flange 42 would it directly against diaphragm 38. In such an arrangement the shield flange 42 prevents the diaphragm 38 from blowing out in case of anexplosion within housing 26. The arrangement shown in the drawings however is preferred since such an arrangement provides a metal to metal seal to contain an explosion.

In order to effectively provide a metal to metal seal to contain an explosion it is necessary that the shield flange 42 conform to wall 39 around the total periphery of opening 40 when forced into such contact by the effect of an explosion. Thus the specific configuration of the forward Wall 39 and the shield flange 42 are not important as long as they substantially conform with each other in the area of contact occasioned by an explosion. For simplicity of manufacture the yarrangement shown wherein the forward wall 39 and the shield liange 42 are both at is the preferred design.

This invention provides a float switch having the highly desirable characteristics of being explosion proof. In addition, the switch is formed of a minimum number of parts, is provided with a pivotal arrangement requiring no rubbing contact points to wear, is provided with a pivotal arrangement such that accumulation of paraffin or corrosion cannot interfere with the free pivotation of the float member and further is provided with a diaphragm including the characteristics of high flexibility plus high resistance to chemical attack, all in a unique manner and at a minimum of material and manufacturing expense and in a manner not shown or suggested by the other types of float switches known.

Throughout this description the switch of the invention has been described as being mounted on the wall of a vessel 12. The term vessel is utilized herein to include any liquid containing enclosure. For instance, a means commonly employed of utilizing the switch includes afixing the switch to a small flow chamber. The ow chamber is normally just large enough to contain and allow the pivotal movement of float 34. The flow chamber is connected by piping to the tank or larger vessel in which the liquid level is to be detected. As the level of the liquid raises or lowers in the larger vessel, the liquid level raises and lowers in the piping containing the flow chamber, actuating the switch in the same manner as if it were affixed directly to the larger vessel.

Although this invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure.

What is claimed:

1. An explosion proof float switch comprising, in cornbination:

a closed explosion-proof chamber having an opening in one wall thereof;

a diaphragm member supported to said wall of said closed chamber, closing the said opening therein;

a rod extending through said opening in said closed chamber and through said diaphragm member, said rod pivotally land sealably supported by said diaphragm member; Y

a float member axed to said rod exteriorly of said closed chamber;

a switch means supported within said chamber actuated by pivotation of said rod;

a shield flange substantially perpendicularly supported to said rod within said closed chamber in near proximity to said opening, said shield ange of an area 'larger than the area of said opening, said shield flange sealably engageable with said wall of said closed chamber around the total periphery of said opening therein when the pressure in said chamber arises.

2. An explosion-proof switch according to claim 1 wherein said shield flange includes an integrally formed switch support leg extending therefrom and wherein said switch includes a mercury switch aixed to said switch support leg.

3. An explosion-proof switch according to claim 1 wherein said shield tlange includes an integrally formed switch leg and an integrally formed stabilizing leg, said legs extending from said shield flange substantially parallel to each other; and including a iirst and a second connection block member, said connection block members spaced apart from each other and supported within said closed chamber, said connection block members supported adjacent and to either side of said shield ange and said shield flange legs whereby said rod is limited by said connection blocks and said shield flange legs to pivotation in one plane.

References Cited by the Examiner UNITED STATES PATENTS BERNARD A. GILHEANY, Primary Examiner. 

1. AN EXPLOSION PROOF FLOAT SWITCH COMPRISING, IN COMBINATION: A CLOSED EXPLOSION-PROOF CHAMBER HAVING AN OPENING IN ONE WALL THEREOF; A DIAPHRAGM MEMBER SUPPORTED TO SAID WALL OF SAID CLOSED CHAMBER, CLOSING THE SAID OPENING THEREIN; A ROD EXTENDING THROUGH SAID OPENING IN SAID CLOSED CHAMBER AND THROUGH SAID DIAPHRAGM MEMBER, SAID ROD PIVOTALLY AND SEALABLY SUPPORTED BY SAID DIAPHRAGM MEMBER; A FLOAT MEMBER AFFIXED TO SAID ROD EXTERIORLY OF SAID CLOSED CHAMBER; A SWITCH MEANS SUPPORTED WITHIN SAID CHAMBER ACTUATED BY PIVOTATION OF SAID ROD; A SHIELD FLANGE SUBSTANTIALLY PERPENDICULARLY SUPPORTED TO SAID ROD WITHIN SAID CLOSED CHAMBER IN NEAR PROXIMITY TO SAID OPENING, SAID SHIELD FLANGE OF AN AREA LARGER THAN THE AREA OF SAID OPENING, SAID SHIELD FLANGE SEALABLY ENGAGEABLE WITH SAID WALL OF SAID CLOSED CHAMBER AROUND THE TOTAL PERIPHERY OF SAID OEPNING THEREIN WHEN THE PRESSURE IN SAID CHAMBER ARISES. 